1. Field of the Invention
This invention relates to an improvement in the formulation of dough-based fried snack foods, especially products made from potato flakes.
2. Background Art
Food preservation is a long practiced art, made necessary by the seasonal nature of most cultivated crops, the action of cellular enzymes, the ubiquity of mycobacteria, insects and rodents, and by the economic advantage obtained by shipping foodstuffs from fertile growing areas to locations of greatest demand. The preparation of peserved foods frequently entails certain steps necessary to return the food to its normal appearance and taste. For centuries, potatoes have been a staple in the diet of Europeans and Americans. Whole potatoes were stored in cool buildings and cellars, and cooked by boiling or baking. Chemical changes in the potato, specifically the conversion of starch to reducing sugars and the "greening" due to the formation of chloroplasts, had little effect on the nutritive value or final appearance of the meal. Fried potato foods, such as french fries, shoestring potatoes, and especially potatoe chips, however, are discolored when reducing sugars are present. In the case of potato chips, only certain varieties of potato can be used to make a commercially acceptable chip, and numerous processes have been developed to store and prepare potatoes for slicing.
In recent years, much of the potato crop in the Western United States has been converted to potato flakes or flour. The removal of the water (as much as 80% of the weight of some varieties) makes storage and shipping more convenient and economical. Reconstitution with water produces an acceptable mashed potato, but the formulation of shaped potato products, such as fries or chips, requires the addition of a binder to form a dough, and the implementation of one or more novel process steps. U.S. Pat. Nos. 3,297,450, 3,539,356, 3,687,679, 3,753,735, 3,800,050, 3,935,322, 3,997,684, 3,998,975, 4,005,139, 4,082,855, 4,140,803, 4,221,842, and 4,238,517 are illustrative of various approaches which have been used in forming a fry or chip from a dough. An extrusion or sheeting step is normally required to achieve the required shape and thickness of a fry or chip. The dough must be formulated to be easily spread to the desired thickness, to resist sticking to the belt or roller, to be cleanly cut by a die, and to resist clumping during frying. Frequently, the resultant product lacks the characteristic flavor and mouth feel of a good potato chip made by the traditional methods of slicing, washing, and frying the slice.
"Lecithin" is a generic name for a class of compounds which are mixed esters of glycerol and choline with fatty acids and phosphoric acid. Lecithin is present in eggs, but the predominant product in commerce today is prepared primarily from soybeans. Commercial soybean lecithin also contains cephalins (an analog of lecithin in which ethanolamine or serine is substituted for choline) as well as inositol, phosphatides, carbohydrates and traces of other substances. Lecithin is readily soluble in mineral oil but poorly soluble in vegetable oils. It is insoluble in water but forms an emulsion with water in certain concentrations. One use of soybean lecithin is as an emulsifying agent in oleomargarine and mayonnaise. Lecithin is also added in small amounts in doughs for baking, but is not used for doughs which are fried in deep fat or oil because the lecithin decomposes at high temperatures to produce free fatty acids among other products. Since many liquid lecithin preparations also include excess free fatty acids to solubilize the lecithin for easier handling (Kirk-Othmer Encyclopedia of the Chemical Industries, Vol. 12, p. 351, 1967 Edition), the use of lecithin in fried foods has historically been avoided, since it causes a buildup of free fatty acids and darkening of the cooking oil. Addition of powdered lecithin to food products that are fried during their production results in rapid free fatty acid increases as well as significant oil darkening rendering the oil unsuitable after only a few hours. Prior to this invention there were no known methods for preventing such deterioration. Products which contain free fatty acids turn rancid quickly and cannot be shipped and stored for an acceptable period of time. As a result, the superior emulsifying properties of lecithin routinely employed by bakers have been unavailable to producers of fried dough-based foods, and less effective chemicals such as monosubstituted glycerides have been substituted, with less satisfactory results.